材料期刊网

用化学共沉淀法制备4.5%Y2O3--ZrO2(YSZ)和0.6% La2O3--YSZ、0.8% La2O3--YSZ、1.2% La2O3--YSZ(0.6La、0.8La、1.2La)(摩尔分数)纳米复合陶瓷粉末, 研究了四组粉末的高温相稳定性。结果表明: 采用正向滴淀方法制备的0.6La粉末(粒径~50 nm)团聚严重, 而用反向滴淀方法制备的0.6La粉末(粒径~20 nm), 粉末团聚少; 各组前躯体粉末在600℃煅烧2 h后都呈单一四方相结构; 在1200℃烧结100 h后0.6La、0.8La坯体呈单一四方相结构, 无相变, YSZ和1.2La坯体都有立方相且1.2La坯体有锆酸镧相生成; 在1300℃烧结100 h后0.6La, 0.8La, 1.2La坯体呈四方相和立方相结构, 其中1.2La坯体有锆酸镧相生成, 在相同条件下烧结的YSZ坯体有少量(~1.5\%)单斜相产生; 在1400℃烧结100 h后各组份中四方相已不能保持稳定, 转化为单斜相和立方相, 0.6La、0.8La、1.2La、YSZ坯体单斜相含量分别为30.5%, 32%, 35%, 46.0%。在YSZ中添加少量La2O3在1300℃烧结能有效改善其高温相的稳定性。

4.5%Y2O3–ZrO2, 0.6%La2O3–YSZ, 0.8%La2O3–YSZ, 1.2%La2O3–YSZ (YSZ, 0.6La, 0.8La, 1.2La) (molar fraction) composite ceramic nanopowders were prepared by co–precipitation method using ZrOCl2·8H2O, Y(NO3)3·6H2O, La2O3 as raw materials. The synthesized powders were characterized and the phase stability was investigated. The results show that the size of 0.6La particles prepared by reverse titration method is ∼20 nm, and the size of particles prepared by the straight titration method is ∼50 nm. The agglomeration of the powder prepared by reverse titration method is also smaller than that of the powder prepared by straight titration method. After calcined at 600^oC for 2 h, all of the synthesized powders showed the pure tetragonal structure; after sintered at 1200^oC  for 100  h, 0.6La, 0.8La showed the pure tetragonal structure, the cubic phase composed of both of YSZ and 1.2La and pyrochlore structure compose of 1.2La; after sintered at 1300 for 100 h, 0.6La, 0.8La, 1.2La showed the tetragonal structure, the cubic phase compose of all synthesized powders and pyrochlore structure compose of 1.2La and small fraction of monoclinic phase (∼1.5%) was formed of YSZ; after sintered at 1400^oC  for 100h, the tetragonal phase cannot keep stable, monoclinic phase compose of all the synthesized powders, the monoclinic phase content of 0.6La, 0.8La, 1.2La, YSZ is 30.5%, 32%, 35%, 46.0% respectively. The phase stability of YSZ can be modified by addition small fraction of La2O3 at 1300^oC.